Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$26.89	10.116%	$29.6102	$29.61	$29.60	$29.60
Purchase #2	$177.66	4.598%	$185.8288	$185.83	$185.85	$185.80
Purchase #3	$193.81	11.693%	$216.4722	$216.47	$216.45	$216.50
Purchase #4	$163.34	13.746%	$185.7927	$185.79	$185.80	$185.80
Purchase #5	$232.72	5.270%	$244.9843	$244.98	$245.00	$245.00
Purchase #6	$120.41	13.762%	$136.9808	$136.98	$137.00	$137.00
Purchase #7	$165.95	9.390%	$181.5327	$181.53	$181.55	$181.50
7 purchase totals =	$1,080.78		$1,181.2017	$1,181.19	$1,181.25	$1,181.20